In celebration of the Earth Day, G5 Entertainment has lowered the price of award-winning strategy game, Build-a-lot 4: Power Source, to a mere $0.99 on iPhone and $1.99 on iPad.

Build-a-lot series has become one of the most popular casual games on the market and an absolute must have for fans of time management/city building sim games. Upon its initial launch, Build-a-lot 4: Power Source has topped all casual game charts; the iOS version of the game made it into the Quality Index’s Top 10 games list of December 2012. Now, for the whole week, players can get this “green” building hit at up to 70% off on their favorite device.

After learning how to construct homes, malls and restaurants, it’s time for you to invest in green energy. In Build-a-lot 4, you’ll be building solar towers, wind farms and even nuclear power plants to make your cities sustainable and prosperous for generations. Watch out for blackouts, though, as building too fast can result in a system overload. So take it slow, plan ahead and manage your energy resources carefully. If your buildings are not supplied with enough energy, the whole neighborhood will remain without electricity and you won’t be able to collect any rent.

Also, keep in mind that wind farms have the smallest negative footprint, while nuclear plants have a correspondingly massive negative impact on the community, but produce much more energy. You will need to keep an eye on the list of goals, and use your strategic thinking to complete each task, while overseeing power reserves, neighborhood appeal, materials and condition of houses. To “go green”, your neighborhoods need eco-chic shops, solar-heated swimming pools, bike paths and more. The game provides hours of strategic game play with 68 levels and tons of goals to complete. Casual and Campaign modes let you enjoy Build-a-lot 4: Power Source at your own pace. Variety of campaigns to work your way through — Tutorial, Main, Challenge and Expert modes will prolong the game life and offer tons of replay value.